Presentation API: implement .getAvalability() (Blink side).

Source/modules/presentation/PresentationAvailabilityCallback.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef PresentationAvailabilityCallback_h
+#define PresentationAvailabilityCallback_h
+
+#include "platform/heap/Handle.h"
+#include "public/platform/WebCallbacks.h"
+#include "wtf/Noncopyable.h"
+
+namespace blink {
+
+class ScriptPromiseResolver;
+
+using WebPresentationAvailabilityCallbacks = WebCallbacks<bool, void>;
+
+// PresentationAvailabilityCallback is an implementation of
+// WebPresentationAvailabilityCallbacks that will resolve the underlying promise
+// depending on the result passed to the callback.
+class PresentationAvailabilityCallback final
+    : public WebPresentationAvailabilityCallbacks {
+    WTF_MAKE_NONCOPYABLE(PresentationAvailabilityCallback);
+public:
+    explicit PresentationAvailabilityCallback(PassRefPtrWillBeRawPtr<ScriptPromiseResolver>);
+    virtual ~PresentationAvailabilityCallback() = default;
+
+    void onSuccess(bool*) override;
+    void onError() override;
+
+private:
+    RefPtrWillBePersistent<ScriptPromiseResolver> m_resolver;
+};
+
+} // namespace blink
+
+#endif // PresentationAvailabilityCallback_h